A very important characteristic of fuel cell power plants is the reliable lifetime of the fuel cell stack itself. In fuel cell stacks employing proton exchange membranes, the end of useful life is usually related to failure of the membrane. Membrane failure adjacent to the air inlet has been determined to be a specific problem which is not uncommon. Dryness of the membrane within the active area promotes membrane failure.
Humidification of reactant gases at the inlet of the gases to the reactant gas flow field channels has been achieved heretofore by humidifying a gas prior to entry into the fuel cell stack. However, the use of external humidification increases the amount of hardware required to accompany the fuel cell stack, which may be impermissible in mobile applications of fuel cells. Humidification has been achieved also by rendering a portion of the fuel cell planform inoperative near the inlets, so that the area will be inactive, and the fuel cell process will not involve a dry membrane. On the other hand, rendering a portion of a fuel cell inactive near a reactant inlet reduces the power density of the fuel cell stack.
Improved humidification of fuel and oxidant gases also usually improves cell performance and extends membrane life.